Circadian variation in the response to the glucose challenge test in pregnancy: implications for screening for gestational diabetes mellitus.

Abstract

OBJECTIVE:

A common approach to screening for gestational diabetes mellitus (GDM) is the universal testing of all pregnant women with a 1-h, 50-g glucose challenge test (GCT), followed by a diagnostic oral glucose tolerance test (OGTT) in those in whom the GCT is positive (≥7.8 mmol/L). More important, the GCT is performed at any time of day, but there has been limited study of the effect of time of day on test performance. Thus, using their subsequent OGTT (performed in the morning), we sought to characterize the metabolic function of women with positive GCTs in relation to the timing of their test.

RESEARCH DESIGN AND METHODS:

A total of 927 women with positive GCTs underwent a 3-h 100-g OGTT. They were stratified into four groups by time of day (hours) of their GCT: <0900 (n = 171), 0900-1059 (n = 288), 1100-1259 (n = 189), and ≥1300 (n = 279).

Comparison of adjusted mean levels of AUCgluc (A), ISOGTT (B), and ISSI-2 (C) among study groups defined by time of day of GCT. All analyses adjusted for age, weeks’ gestation at OGTT, prepregnancy BMI, weight gain up to OGTT, family history of diabetes, ethnicity, parity, and previous GDM. The error bars show the SE.

Prevalence of glucose tolerance categories on OGTT (GDM, GIGT, and NGT) within each GCT group in (A) the entire study population (n = 927) and (B) in those subjects who would be diagnosed with GDM on the basis of GCT >10.3 mmol/L (n = 22).